The present invention generally relates to dilation systems and related methods of their use. The systems and methods are for gaining access to portions of a patient""s body by a physician, for example to obtain percutaneous access to the kidney by a urologist or a radiologist for nephrolithotomy. In particular, the present invention relates to dilation systems throughout the length of the opening and methods for dilating a track opening to a desired size and maintaining that opening with a single device.
Current procedures for forming a track in a patient involve first piercing the flank of the patient and, for example, the kidney with a small needle for initial access. Proper imaging verifies the correct placement. The track is then opened to a desired size by any of a variety of methods.
In a first method, a balloon catheter, back loaded with a sheath, is inflated to an appropriate pressure. This pressure provides the radial force to dilate the track. After the track is dilated, a sheath is passed over the balloon to maintain the track opening. For different track sizes, an array of balloons of varying sizes are needed because the maximum dilation force is obtained only when the balloon is fully inflated. For each different size balloon catheter, a different sized sheath must be used. This method of dilation, however, as opposed to the second method of renal dilators and sheaths, provides equal radial force around the circumference of the balloon and along its length (so called xe2x80x9ccontinuous dilationxe2x80x9d). It is generally preferred for this reason and because it minimizes trauma to the patient. However, balloons are prone to inflate with irregularities when the resistance of the surrounding tissues is irregular such as encountered with segments of scar tissues. The weakest area of the tissue is dilated faster forming a waist, the remaining tissue is dilated as the inflation pressure is increased, but at a slower rate. This phenomenon is referred to as xe2x80x9cwaisting.xe2x80x9d
A second currently used method of dilation involves the use of several passive renal dilator and sheaths. The renal dilator shears tissue as it is introduced into the track. The passive dilator is a plastic tube with a bullet tip; the passive sheath is a hollow tube. Both dilators and sheaths have specific preset diameters. For example, the size of renal dilators range in diameter from 8 F to 30 F in increments of about 2 F (F refers to xe2x80x9cFrench,xe2x80x9d a unit of measurement of diameter, where 1 F=0.013 inch). An 8 F dilator is first used to dilate the track, followed by substitution of incrementally larger dilators until the desired track size is obtained. Thus, multiple exchanges of dilators are necessary. This method causes undesirable shearing of tissue.
In a third method, an elongate tube made of elastic material such as rubber is mounted and stretched longitudinally onto a rod, thus decreasing the radial size of the tube. The mounted tube is inserted into a track opening and released from the rod, thus increasing the radial size of the tube to its original size. Using this system, one needs a series of tubes having varying radial sizes to fit the desired track opening. Selection of the desired size tube permits the dilation of a track opening in one step. However once a tube is selected and positioned, the size of the track cannot be modified.
In a fourth method, the dilators have a tapered distal end formed by a compacted slit tube or a series of foil wrapped onto one another to form a cone which may be gradually expanded by manual insertion of a rod within the interior of the dilator until the wall of the dilator""s distal end have become parallel.
In yet another method, a mesh tube is introduced percutaneously in the body using a needle and stylet. Once placed into the body, the needle and the stylet are removed from the mesh and a passive dilator is inserted manually to expand the radius of the mesh tube. Using this system, still several passive dilators are needed to gradually reached the desired track size.
A major inconvenience of these methods is that for each desired track diameter, one must use a specific dilator or balloon and a specific sheath. The limited availability of sizes for these components limits the availability of track sizes that maybe obtained. Further, once these components are inserted, the track size cannot be constricted.
To overcome the deficiencies of these methods, the present invention provides dilation systems and related methods in which progressive dilation to a desired track size is accomplished using an actuation device with a dial-a-size functionality integrated into a single device. Further, dilation to a desired track size and maintenance of the track opening are also integrated into a single device. The integrated device provides increased versatility and flexibility to the physician. Further, the dilation systems of the present invention provides for the homogeneous application of radial forces along the length of the dilating element, and homogeneous resistance against countering radial forces applied to the dilating element by the more or less compliant surrounding tissues of the body opening into which the dilating element is inserted. Several dilation systems are presented in the detailed description that follows which combine in a variety of ways various dilating elements and actuation mechanisms. The elements of each of the systems described specifically hereinafter may be combined with one another to achieve other acceptable dilation systems that result in functionally similar devices.
In one aspect of the invention, the dilation systems includes a dilating element and an actuation mechanism, the latter interfaces between the dilating element and the user. The dilating element can be radially expanded to any of a plurality of diameters. The dilation of the dilating element is directed and controlled by the actuation mechanism. Similarly, once dilated, the dilating element may be radially constricted to any of a plurality of diameter using the actuation mechanism.
In one embodiment of the dilation system, the dilating element is a rolled foil. The rolled foil may be used alone or in combination with other dilating elements. The rolled foil develops radial outward forces when compressed to a diameter smaller than its original resting diameter and inward radial forces when dilated larger than its original resting diameter. When used from an initial compressed state the rolled foil is preferably used as a dilating element and also as a sheath once in the dilated state. When used from an initial resting state to a dilated state the foil is preferably used as a sheath in combination with another dilating element of the invention. Other embodiments of the dilating elements suitable for use in combination with the rolled foil are, but not limited to, the following: malecots; jacks; parallelograms; balloons; wire baskets; pivots; telescopic cannulas, chain links; longitudinal springs, meshes and braids. These elements may be used as a single unit or a series of them arranged head-to-tail, within the rolled foil. In one embodiment, two rolled foils may be used as dilating element, one in a compressed state contained within the lumen of the other one, the other one in the resting state.
In another embodiment, the rolled foil includes a series of locking mechanisms that permits the selection and retention of a variety of dilated or compressed diameters.
In one embodiment the locking mechanisms includes two series of interfitting structures, one series is located on a segment of the foil, the other series is located on a second segment of the foil spatially proximal to the first series. The series of intermitting structure may be bumps and notches, protrusions and recesses, tongues and recesses, tongues and holes, and rivets and holes. In another embodiment, the locking mechanism further includes a trigger which interfaces between the two series of interfitting structures to facilitate the locking and releasing of the locking mechanism by engaging or disengaging of the one series of interfitting structure vis-a-vis the other. In one embodiment, the locking mechanism provides the locking of motion unidirectionally to prevent for example either excessive dilation or deflation of the dilating element. In another embodiment, the locking mechanism provides the locking of motion bidirectionally.
Certain embodiments of the dilating element provide dilation along a certain length of a track of a body without forming a waist. Waistless dilating elements include a combination of a hard or noncompliant expandable cover with a variety of dilating elements. Hard or non-compliant expandable covers include, but are not limited to, the following: rolled foils, meshes and braids. Suitable dilating elements include, but are not limited to, any one, or a series of one, of the following: malecots; jacks; chain links; longitudinal springs; parallelograms; balloons; wire baskets; telescopic cannulas, and pivots. A preferred embodiment at least includes a rolled foil. Another preferred embodiment includes a balloon covered by a mesh or braid.
In other preferred embodiments, the dilating element is covered by other expandable sheaths, such as expandable membranes, nonexpandable membranes may also be used as sheath but require to be compacted on the deflated dilating element.
The actuating mechanism includes a dial and a transmission mechanism. The dial and the proximal end of the transmission mechanism are housed in a handle. The handle and the dial includes a series of markings or indices graduated preferably in unit of French or other suitably unit proportional to the diameter of the dilating element. The dial can occupy a variety of configurations in relation to the handle, each configuration identified by a different index and for selection by the user. The dial is connected to the proximal end of the transmission mechanism within the handle. In some embodiments, the dial is connected directly to the transmission mechanism, if no amplification of motion is required. In some other embodiments the dial is indirectly connected to the transmission mechanism, through an amplifying mechanical structure.
Also in some embodiments, the dial is directly actuated by the user and transfer motions from the user to the transmission mechanism. Yet in other embodiments, the dial indirectly transfers motions from the user to the transmission mechanism. For example, the dial includes an electronic interface which include, but is not limited to, a power source, a circuitry, a series of switches, and a motor connected to the transmission mechanism.
In some embodiments, the transmission mechanism transfers a motion of the dial to the dilating element. The motion may either be longitudinal or rotational. In these embodiments, the transmission mechanism includes at least one tubular member such as, but not limited to, cannulas, rods, shafts, or needles.
In some other embodiments the transmission mechanism converts and transfers motions from the dial to the dilating element. In these embodiments the transmission mechanism includes at least a tubular member and at least one thread. In some other embodiments the tubular member includes two threads. In certain embodiments one thread is located at the proximal end of the tubular member for engagement with the dial, the other at the distal end for engagement with the dilating element. In other embodiments, the two threads are located in the distal end, one for engagement with the proximal end of the dilating element, the other for engagement with the distal end of the dilating element.
In another aspect, the invention is directed to methods for dilating a track of a body. In one embodiment the method includes the following steps: insertion in the track of a dilating element capable of expanding to any of a plurality of diameters; expansion of the dilating element to any of a plurality of diameters. The expansion of the dilating element is controlled by the user which actuates the actuation mechanism. In other embodiments, the methods also include the step of introducing a sheath over the dilating element in a dilated state to maintain the track dilated to the diameter selected from the plurality of diameters. Yet other embodiments of the methods include the step of removing the dilating element from the track.
Alternatively, the dilating element may be removed after having been deflated to any of a plurality of diameter inferior to the diameter of the dilated state.
In certain embodiments of the methods according to this invention, the dilating element is first inserted into the track of a body and then dilated. Yet in other embodiments, the dilating element is first dilated, then inserted into the track of a body in the dilated state.
Additional objects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate several embodiments of the invention and together with the description, serve to explain the principles of the invention.